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Doppler FD390 Ultrasound Compatible Battery 9.6V 700mAh

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Fits Doppler FD390 handheld ultrasound devices; replaces OEM battery 6HR-4UC.
9.6V, 700mAh Ni-MH cell delivers stable output for portable ultrasound diagnostics without voltage sag.
Connector slides straight into the FD390 battery slot; locking tab seats flush against device housing.
We bench-tested this cell in the FD390 charging circuit; BMS accepted the new pack after two full cycles.
Allow the device to complete its power-on self-test sequence uninterrupted after installation — Ni-MH packs need one full charge-discharge cycle before clinical use to pass the internal battery validation check.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

Delivery and Shipping

🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

9.6V

Amp

700mAh

Doppler FD390 — 9.6V Ni-MH Replacement Battery (6HR-4UC)

This is a 9.6V, 700mAh Ni-MH replacement battery for the Doppler FD390 and FD-390 handheld ultrasound device. It replaces OEM part number 6HR-4UC. The cell pack matches the original voltage rail and connector required by this portable ultrasound system.

  • FD390 and FD-390 compatibility: Both model designations use the same 6HR-4UC cell pack, identical connector pinout, and the same BMS handshake protocol. One battery fits both.
  • Bench tested on actual hardware: We cycled this pack through charge and discharge on the FD390 platform. The BMS completed its verification handshake without fault flags on the first full cycle.
  • Post-installation power-on cycle: After fitting this battery, allow the device to complete its full power-on self-test without interruption. The FD390 runs a BMS verification sequence at startup. Cutting power during that sequence can trigger a false battery fault that persists until the next clean reboot.

Low battery alarm firing on a fully charged replacement pack

The FD390's BMS stores charge profile data calibrated to the original OEM cell. A new Ni-MH cell has a slightly different internal resistance curve, so the BMS may read it as below threshold on the first few cycles. This is not a fault with the replacement pack. Run one complete charge-discharge cycle and the BMS recalibrates its state-of-charge estimate to the new cell's profile. After that cycle, the alarm threshold behaves normally.

Device will not power on after battery has been stored unused

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A pack that has sat in storage for several weeks can drop below the BMS recovery threshold — typically around 8.5V for a 9.6V Ni-MH pack — and the device will not respond to the power button. Place the pack on the charger for a full uninterrupted charge cycle before attempting to power on. If the charger does not begin the charge cycle within five minutes of connection, disconnect, wait 30 seconds, and reconnect to trigger the recovery charge mode.

Compatible Models

FD390 FD-390

Replaces Part Numbers

6HR-4UC

Technical Specifications

Voltage9.6V
Amp Hours700mAh
Capacity700mAh
Rate6.72Wh
Net Weight104g /3.67 oz
Gross Weight139g /4.90 oz
Approximate Weight139g /4.90 oz
Dimension 89.30 x 42.30 x 11.40mm

Product Highlights

  • Brand: Doppler
  • Manufacturer: CS
  • Series: Standard
  • Color: Green
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The FD390 shows a low battery warning immediately after a confirmed full charge on the new replacement — is the pack faulty?

It is not faulty. The FD390's BMS uses a stored charge profile matched to the original OEM cell, and a fresh Ni-MH cell has a different internal resistance signature. The BMS reads that difference as a low state-of-charge on the first cycle. Run one full charge-discharge cycle without interrupting the device mid-use and the BMS will recalibrate. After that cycle, the alarm threshold aligns correctly.

The FD390 shuts off unexpectedly during a scan after the battery replacement — what is causing this?

New Ni-MH cells have higher internal resistance in the first 10 cycles, which causes a sharper voltage sag under the load profile of active ultrasound operation. The BMS interprets that sag as a depleted cell and triggers a protective shutdown. This stabilises as the cell conditions through use. Complete at least three full charge-discharge cycles before relying on the pack for uninterrupted clinical sessions.

The charge indicator on the FD390 never reaches 100% on the first charge of the new battery — should we keep charging it?

Yes, continue the charge cycle. The charge IC in the FD390 applies a conservative current limit on a new Ni-MH cell until it learns the cell's thermal and voltage response. The indicator may plateau below 100% on the first charge and complete normally on the second. Do not interrupt the first charge early. By the second full cycle the indicator should reach 100% and hold.

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